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Home > Products > Discrete Semiconductor Products > Transistors > Bipolar (BJT) > Single Bipolar Transistors

STMicroelectronics BU931P

Name: BU931P
Brand: STMicroelectronics
SKU: BU931P
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BU931P

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: TO-247-3

Datasheet:: BU931P.pdf

Description:: TRANS NPN DARL 400V 15A TO-247-3

Quantity:: RFQ Add To RFQ list

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Product details

Overview

BU931P from STMicroelectronics is an automotive-grade NPN power Darlington transistor designed as a high-voltage ignition coil driver, featuring V_CEO = 400 V, I_C = 10 A, and T_j up to 175 °C, with AEC-Q101 qualification for under-hood electronic ignition systems.

For engineers reviewing the BU931P datasheet, BU931P pinout, BU931P application, or BU931P equivalent, key selection criteria include ruggedness under inductive switching stress, safe operating area at elevated junction temperature, and compliance with automotive ignition transient voltage requirements (e.g., load dump, ISO 7637-2).

Technical Context

The BU931P employs multi-epitaxial planar bipolar technology optimized for high-energy inductive load switching. Its internal structure integrates a monolithic Darlington pair with integrated base-emitter clamp diode, enabling robust turn-off under high dV/dt conditions typical of ignition coil flyback.

It operates in linear and saturated switching modes with specified V_CE(sat) ≤ 1.8 V at I_C = 10 A / I_B = 250 mA and supports pulse operation up to 20 A peak collector current with ≤2% duty cycle, validated per AEC-Q101 stress test profiles.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	400 V - Sustaining voltage under zero-base-current condition; defines maximum inductive flyback voltage tolerance before breakdown
I_C	10 A continuous - Rated collector current at T_c = 25 °C; derates linearly above case temperature
P_TOT	125 W at T_c = 25 °C - Total power dissipation limit; requires heatsink for sustained operation above ~40 °C case temp
R_thJC	1.2 °C/W - Junction-to-case thermal resistance; enables thermal design using measured case temperature
h_FE	300 min at I_C = 5 A - DC current gain ensures low base drive requirement for full saturation at rated load
t_s + t_f	< 15.5 μs - Storage + fall time with R_BE = 47 Ω; critical for minimizing energy loss during coil de-energization
T_j max	175 °C - Maximum operating junction temperature; qualified per AEC-Q101 for under-hood automotive environments

Pinout & Package

BU931P is housed in TO-220 type A package with isolated tab (collector-connected), standard 3-pin vertical mounting configuration. The metal tab serves as the collector terminal and must be electrically isolated from heatsink unless system grounding scheme permits direct connection.

Pin/Terminal	Circuit Role	Design Meaning
Collector (Tab)	Main power output path	Electrically connected to metal tab; requires insulated mounting hardware when referenced to non-collector potential
Base	Control input	Drives Darlington pair; requires current-limited source (e.g., 70–250 mA) for full saturation at 10 A load
Emitter	Power return path	Low-side return node; connects to ground or low-side switch; carries full load current

Key Features

Feature	Design Value
AEC-Q101 qualification	Validated for automotive under-hood use including temperature cycling, humidity, and mechanical shock per Rev G
High V_CEO(sus)	400 V sustaining voltage ensures reliable operation during 300 V clamp events in 12 V ignition systems
Integrated clamp diode	Monolithic emitter-base diode limits reverse base-emitter voltage to 5 V, preventing B-E junction failure during flyback
Rugged SOA	Safe operating area supports 10 A × 400 V for ≥10 ms pulses, covering worst-case ignition dwell/flyback transients
TO-220 isolation	Electrically isolated tab allows flexible mounting without additional insulating hardware in grounded-collector configurations

Applications

Gasoline Engine Ignition

Distributorless Ignition Systems (DIS)

Use Scenario: Direct drive of primary winding in coil-on-plug (COP) or coil-near-plug (CNP) units in 4–12 cylinder engines.

IC Role / Device Role / Timing Role: High-current, high-voltage switch controlling dwell time and energy delivery to ignition coil.

Use Value: Enables precise spark timing control with <15.5 μs turn-off delay, reducing misfire risk at high RPM.

Use Scenario: Dual-coil modules driving paired cylinders in waste-spark DIS architectures.

IC Role / Device Role / Timing Role: Primary-side power switch synchronized to crank/cam signals via external controller.

Use Value: Supports 20 A peak current for dual-coil simultaneous firing while maintaining <1.8 V saturation drop.

Heavy-Duty Diesel Preheat Control

Two-Stroke Marine Engine Ignition

Use Scenario: Switching glow plug preheat circuits in commercial diesel engines with extended dwell periods.

IC Role / Device Role / Timing Role: High-duty-cycle linear regulator for controlled current ramp into resistive glow plugs.

Use Value: 175 °C T_j rating and 125 W dissipation allow sustained 10 A operation without thermal shutdown.

Use Scenario: Compact ignition drivers in outboard marine engines exposed to salt fog and vibration.

IC Role / Device Role / Timing Role: Ruggedized switching element interfacing microcontroller PWM to high-inductance coils.

Use Value: AEC-Q101 qualification and TO-220 isolation ensure reliability in harsh marine EMI/thermal environments.

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-voltage ignition switching applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
BU931T	Same die, TO-220 package with non-isolated tab; R_thJC = 1.2 °C/W identical; no ECOPACK® marking	Requires insulating kit for grounded heatsinks; otherwise functionally identical in ignition circuits	Select BU931T only if tab isolation is managed externally and RoHS compliance is not required
STGD10NB60S	600 V, 10 A N-channel MOSFET; gate-driven, no base current; R_DS(on) = 0.6 Ω vs. V_CE(sat) = 1.8 V	Needs gate driver IC and overvoltage protection; lower conduction loss but higher EMI during switching	Choose for efficiency-critical designs with available gate drive resources and layout control for dv/dt noise

Compared with BU931T, the BU931P offers factory-insulated tab for simplified thermal mounting; versus STGD10NB60S, it eliminates gate drive complexity and provides inherent ruggedness against voltage transients without external clamping.

Availability

BU931P is available at Aetrix Electronics and suitable for gasoline engine ignition modules, distributorless ignition systems (DIS), and heavy-duty diesel preheat controllers requiring stable component supply across automotive production lifecycles.

Supply support for BU931P includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

STMicroelectronics is a global semiconductor leader headquartered in Geneva, specializing in automotive, industrial, and power discrete technologies with broad manufacturing and qualification infrastructure.

The BU931P belongs to ST's automotive-qualified power transistor family, engineered specifically for high-reliability, high-energy switching in engine management systems where thermal resilience and transient immunity are critical.

FAQ

Is BU931P pin-compatible with BU931T?

Yes - BU931P and BU931T share identical TO-220 pinout (Collector–Base–Emitter) and electrical specifications. The sole difference is BU931P's electrically isolated tab, which eliminates need for mica washers when mounted to grounded heatsinks.

What is the recommended base drive circuit for BU931P in ignition applications?

A current-limited base driver delivering 70–250 mA is required. Typical implementation uses a 12 V logic-level signal through a 47 Ω series resistor and optional base-emitter clamp (e.g., 5.1 V Zener) to prevent reverse bias during flyback.

Does BU931P require a heatsink in continuous 10 A operation?

Yes - at 10 A and V_CE(sat) ≈ 1.8 V, power dissipation exceeds 18 W. With R_thJC = 1.2 °C/W, even modest ambient temperatures necessitate a heatsink to maintain T_j ≤ 175 °C; thermal interface material and mounting torque are critical.

Can BU931P replace BU931 in legacy designs?

No - BU931 was packaged in TO-247 and discontinued in 2008. BU931P is not a drop-in replacement due to different footprint, thermal path, and mounting hole pattern; redesign of PCB and mechanical interface is required.

BU931P Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: TO-247-3

Packaging:: Tube

Product Status:: Active

Transistor Type:: NPN - Darlington

Current - Collector (Ic) (Max):: 15 A

Voltage - Collector Emitter Breakdown (Max):: 400 V

Vce Saturation (Max) @ Ib, Ic:: 1.8V @ 250mA, 10A

Current - Collector Cutoff (Max):: 100µA

DC Current Gain (hFE) (Min) @ Ic, Vce:: 300 @ 5A, 10V

Power - Max:: 135 W

Frequency - Transition:: -

Operating Temperature:: 175°C (TJ)

Grade:: Automotive

Qualification:: AEC-Q101

Mounting Type:: Through Hole

Supplier Device Package:: TO-247-3

BU931P FAQ

1.How can I place an order for BU931P through Aetrix?

Please submit a Request for Quotation (RFQ) for BU931P on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for BU931P reliable?

The price and inventory of BU931P are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BU931P is usually 5 days.

3.What payment methods are accepted for BU931P?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BU931P transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BU931P?

BU931P orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BU931P order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for BU931P?

For technical support, including BU931P datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BU931P requirements.

6.How does Aetrix verify that BU931P is sourced from the original manufacturer or authorized distributors?

All BU931P products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that BU931P meets industry standards.

7.What is the process for return or replacement of BU931P?

All BU931P units undergo pre-shipment inspection (PSI). If there is an issue with BU931P, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The BU931P part is unused and in its original packaging.

Return procedure for BU931P:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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